What a post-money SAFE means on paper

Post-money SAFE explained in plain terms: a post-money SAFE is a short contract for cash now and shares later, with a valuation cap stated as a post-money valuation so ownership sold is transparent as investment amount divided by that cap. Y Combinator's SAFE documents page (checked 31 Oct 2026) says the post-money SAFE has been the YC standard since 2018, that conversion in an equity financing is automatic, and that a SAFE is not debt (no interest, no maturity on the standard form). This post is educational, not legal advice. Confirm forms and jurisdiction with counsel before you sign or send anything.

Post-money SAFE explained as ownership you can calculate

On a post-money valuation-cap SAFE, YC describes ownership sold as the investment divided by the valuation cap. That is the core reason founders and investors like the form: you can talk about percent sold before the priced round happens, instead of waiting for conversion math nobody can agree on in a meeting.

The figures in this section are an illustrative example only. They are not a real company raise, not a signed SAFE, and not advice on what your cap should be.

Imagine you target $1,000,000 of SAFE cash and are willing to sell about 15 percent on a post-money basis. Cap = $1,000,000 ÷ 0.15 ≈ $6,700,000. Raise $500,000 on that same cap and you sell about 7.5 percent. Raise $800,000 and you sell about 12 percent. YC's documents page walks the same style of example; replace every number with your own target raise and ownership budget before you quote a cap to anyone.

You can also raise on more than one cap. An illustrative stack: $500,000 at a $5,500,000 cap (~9 percent) plus $500,000 at an $8,300,000 cap (~6 percent) lands near 15 percent sold in total if you sum post-money ownership that way. Model the stack before the second paper goes out, because later SAFEs do not rewrite the first investor's locked percent the way founders sometimes hope.

What the word "post" includes and excludes

YC explains that a post-money valuation and a pre-money valuation frame the same company valuation at different points in time. Pre-money is immediately before the investment. Post-money is immediately after. On the post-money SAFE, the valuation cap is "post" the money you raise on SAFEs. It is not also "post" the later equity financing money. YC also states the post-money valuation cap is "post" options and the option pool existing before the equity financing, and is not also "post" a new or increased option pool adopted as part of that financing. Read the current form and primer; do not rely on memory of an older template.

That distinction matters when someone says "we already sold 20 percent on SAFEs, so Series A dilution is light." The priced round can still add preferred shares and a pool top-up that dilute everyone further on a fully diluted view. Track convertibles early so the surprise is not in diligence.

Forms you will actually see

YC publishes three US post-money SAFE versions (valuation cap, discount, MFN) plus an optional side letter. Non-US forms exist for some jurisdictions; the Send a SAFE tool on YC's site supports US-incorporated companies as of the page checked 31 Oct 2026. Companies formed elsewhere should use counsel and the matching downloadable forms. Keep the SAFE unmodified when you can. Put extra rights in a side letter counsel drafts instead of editing the SAFE body.

An MFN SAFE adopts more favorable terms from a later SAFE. YC notes the date that matters is the later of signing or receiving the wire, not when you sent the draft. Close lower-cap SAFEs that are fully wired before you issue an uncapped MFN if you want to control that sequence. There is no separate uncapped form: YC says to use the discount form with Discount Rate set to 100 percent when you want no valuation cap.

When it converts, and what it is not

When the company sells preferred stock in an equity financing, outstanding SAFEs convert under the form's rules. YC states conversion in an equity financing is automatic for the post-money SAFE framework it publishes, and that there is no threshold raise amount required to trigger conversion. The SAFE holder does not get a veto on that conversion; the instrument is meant to turn holders into stockholders, then terminate.

A SAFE is not debt and not a loan on the standard form: no interest and no maturity date. Convertible notes still exist in the market and behave differently. Know which instrument you signed. A SAFE is also not stock until conversion. On liquidity (acquisition or IPO) and dissolution, the valuation-cap SAFE has its own payout rules in the form (YC summarizes greater of 1x or as-converted common treatment on liquidity for the valuation-cap SAFE, and return of purchase amount on dissolution, junior to debt). Those are orientation points from YC's FAQ; your signed PDF controls.

A SAFE does not expire by calendar maturity. It is designed to end when the investor receives stock (or otherwise under the form). Transfer usually needs company consent except to an affiliate. Amendments need written consent; purchase amount for one investor cannot change without that investor's consent.

Side letters, second checks, and wire mismatches

Pro rata rights let an investor buy into the later equity financing to keep ownership from shrinking. YC puts those rights in an optional standardized side letter, not inside the SAFE itself. It is fine to push back. Evaluate whether the check size justifies the right. YC's own framing: a $500,000 SAFE has a stronger case for pro rata than a $10,000 SAFE. Keep every side letter filed beside the instrument with the same date trail.

If an investor who already signed wants to invest more, YC recommends a separate new SAFE on the same terms rather than amending the first. If the wire is a few dollars off from fees or FX, YC notes the investor technically owes any shortfall and that refunding overpayment while keeping the SAFE amount exact is the clean record; that is not accounting or tax advice. An unfunded signed SAFE is not binding until money is received; follow up with a firm date and treat long silence as void after you document it, then return late money or sign a fresh dated SAFE if funds appear later.

Board approval, accredited investors, and counsel

YC's SAFE FAQ states the board of directors must approve issuing SAFEs, and that SAFE investors should be accredited, with a rescission path discussed if an investor is not accredited at equity financing. Treat those as orientation from YC's public FAQ and confirm with counsel for your jurisdiction and facts. Keep board consent and investor accreditation notes in the same folder as the PDF.

This is still not a substitute for a lawyer licensed where the company was formed. YC disclaims responsibility for use of its forms and Send a SAFE tool and tells you to consult counsel before using them. Nonstandard edits, international entities, and stacked side letters are where DIY copies go wrong.

Record the instrument the day cash hits

The same day funds arrive, write down investor name, SAFE amount, form version (post-money cap, discount, or MFN), valuation cap or discount rate, side letter yes/no, PDF path, wire date, and board consent date. Put the convertible on a fully diluted view so founder percent stories stay honest before the priced round. Cap Table in Nautis tracks stakeholders, share counts, option pool, financing instruments including SAFEs and notes, and scenarios for what future rounds do to ownership. Record equity rounds and instruments on the Equity tab so alerts catch over-issuance against authorized shares. Track the relationship and next steps in Fundraising CRM so the paper trail and the pipeline stay linked.

Before you quote a cap in a meeting, run the math in the free SAFE Note Dilution Calculator: investment, cap, discount if any, post-money vs pre-money, and an honest estimate of the next priced round. Stack multiple post-money SAFEs by modeling each and summing ownership where the tool's guidance says that is appropriate. Overestimating the next valuation makes dilution look lighter than it will feel later.

One composite story (illustrative, not real)

The story below is a composite illustrative example, not a real company or named founders' deal.

Two cofounders raised three post-money SAFEs on the same $8,000,000 cap: $200,000, $250,000, and $300,000. On a napkin they treated "SAFE dilution" as only the last check. On a stacked view, ownership sold on that cap alone was already about 9.4 percent before any Series A shares or pool top-up. They rebuilt the Cap Table with each instrument as its own row, reran the calculator with a conservative next-round pre-money, and only then set the ask for the priced round. Dilution still happened; the surprise did not.

Keep the ask identical across every note

When you are still raising on SAFEs, keep amount, instrument label (post-money SAFE), cap or discount, and timeline identical in every investor note and CRM field. Soft yes and no go in the same day. Do not change the verbal cap after a handshake without revised paper. Do not mix unlabeled pre-money and post-money forms in one data room folder. Do not treat SAFE cash as operating revenue in the P&L story you tell later investors.

Post-money SAFE explained well ends with a dated instrument row you can recompute, a conversion sketch that matches YC's ownership formula for cap SAFEs, side letters filed beside the SAFE, and counsel on anything nonstandard. Use the calculator and Cap Table before the next signature, not after the wire clears.

Related reading on SAFEs (not repeated here)

This post explains the post-money SAFE form: ownership as investment divided by the post-money cap, what "post" includes, and day-of recording. It does not reteach note-versus-SAFE choice or a full SAFE primer. For the SAFE definition, see SAFE note explained for startups. Separate posts cover valuation-cap negotiation and convertible note vs SAFE; those drafts stay unlinked until they are live on the public blog.